Explosive cutting device



p 1968 H.W. HANNAGAN ETAL 3,401,631

EXPLOSIVE CUTTING DEVICE 3 Sheets-Sheet 1 Filed Sept. 16, 1966 Attorneysn m. G n m H W M m H Robert L. Dobrei LIIIIIIIZia l 1968 H. w. HANNAGANETAL 3,401,631

EXPLOSIVE CUTTING DEVICE 3 Sheets-Sheet 2 Filed Sept. 16, 1966 Q5 mm 4 Tm W M. r J O v w M WL 5% 0 f .D a HmM w p 1968 H. w. HANNAGAN ETAL3,401,631

EXPLOSIVE CUTTING DEVICE Filed Sept. 16, 1966 s Sheets-Sheet 3 INVENTORSHarold W Hannagan Robert L. Dobrei Attorneys United States Patent3,401,631 EXPLOSIVE CUTTING DEVICE Harold W. Hannagan, Napa, and RobertL. Dobrei, Fairfield, Calif., assignors to Explosive Technology, Inc.,Fairfield, Calif., a corporation of California Filed Sept. 16, 1966,Ser. No. 580,071 13 Claims. (Cl. 102-24) ABSTRACT OF THE DISCLOSUREExplosive cutting device formed of at least two sections and havingnon-yieldable latching means for securing the free ends of the sectionsand also having safety features to prevent inadvertent firing.

This invention relates to and explosive cutting device and moreparticularly to an explosive cutting device in which explosives areutilized for cutting relatively large objects.

In patent application Ser. No. 481,009, filed Aug. 19, 1965, there isdisclosed an explosive Cutting device. However, it has been found in thecommercialization of an explosive cutting device that it is desirable tosimplify the same and also it is desirable to incorporate additionalsafety features. There is, therefore, a need for a new and improvedexplosive cutting device.

In general, it is an object of the present invention to provide anexplosive cutting device which has additional safety features.

Another object of the invention is to provide an explosive cuttingdevice of the above character which is constructed so that it will notrelease fragments durmg firin Aiother object of the invention is toprovide an explosive cutting device of the above character in whichsafety devices have been incorporated to prevent 1nadvertent firing ofthe explosive cutting device.

Another object of the invention is to provide an explosive cuttingdevice of the above character which cannot be fired when it is not inplace upon the object which is to be cut.

Another object of the invention is to provide an explosive cuttingdevice of the above character in which a completely shielded releasecable is utilized for firing the same.

Another object of the invention is to provide an explosive cuttingdevice of the above character which has been greatly simplified in itsconstruction and which can be economically manufactured.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiment is set forth indetail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a side elevational view of an explosive cutting deviceincorporating the present invention mounted upon a pipe which is to becut.

FIGURE 2 is a cross-sectional view taken along the line 2-2 of FIGURE 1.

FIGURE 3 is a cross-sectional view taken along the line 3--3 of FIGURE2.

FIGURE 4 is a cross-sectional view taken along the line 44 of FIGURE 2.

FIGURE 5 is a cross-sectional view taken along the line 55 of FIGURE 2.

FIGURE 6 is a cross-sectional view taken along the line 66 of FIGURE 2.

FIGURE 7 is a cross-sectional view similar to FIG- URE 6 but showing thefiring mechanism in a fire condition.

3,401,631 Patented Sept. 17, 1968 FIGURE 8 is a cross-sectional viewtaken along the line 8-8 of FIGURE 2.

In general, the explosive cutting device consists of a linear shapedexplosive charge which is wrapped around the tubular object to be cut. Ashield formed of at least two sections is mounted on the tubular objectand encloses the linear shaped explosive charge. The shield is formed sothat it can be split apart so that it can be slipped over an elongateobject. Means is provided for rigidly securing the sections together sothat fragments cannot escape during the explosion. A firing mechanism isprovided on the shield for detonating the linear shaped explosivecharge. A number of other novel features are included in the firingmechanism to prevent accidental firing.

More particularly as shown in the drawings, the explosive cutting deviceconsists of a shield 11 which is formed of two half sections 12 and 13.The half sections 12 and 13 are substantially U-shaped in cross-sectionand have top wall portions 12a and 13a, respectively, and spacedparallel side wall portions 12b and 13b, respectively, to therebyprovide a shield which is open on the inner side. Hinge means 16 isprovided for connecting the two ends of the half sections 12 and 13 andconsists of hinge portions and which are formed integral with thesections 12 and 13. The portions 12c and 13c are interconnected by ahinge pin 17 to thereby permit the sections 12 and 13 to swing about thehinge pin 17 and to permit the same to fit over an object such as pipe21 which is to be cut. The sections 12 and 13 can be formed of asuitable material, as for example, they can be formed by sand castingutilizing a material called Vulcanite which is a spheralyticheat-treatable iron. This material is particularly adavntageous becauseit is stronger than normal cold rolled steel and, in addi tion, thecasting process makes it possible to cast in r inforcing webs 12d and13d, respectively, in sections 12 and 13. As can be seen, thereinforcing webs extend radially and are perpendicular to the side Wallportions 12b and 13b. Overlapping end portions He and 13e are alsoprovided.

When the shield 11 is in position on the pipe 21, the shield incombination with the pipe 21 forms an annular chamber 22 which encirclesthe pipe 21. A flexible linearshaped explosive charge 23 is disposedwithin the chamber 22 and encircles the object to be cut. Thelinear-shaped explosive charge can be of any suitable type. For example,it can be of the type marketed under the trademark Jetcord by ExplosiveTechnology, Inc. of Fairfield, Calif. As is well known to those skilledin the art, such a linear-shaped explosive charge consists of a shapedmetal member 27 of a suitable material such as lead which issubstantially V-shaped or chevron-shaped in cross-section to concentratethe explosive effects. The open side of the V or chevron is positionedso that it faces in the direction in which the cut is to be made in theobject. An explosive charge 24 is embedded within the metal member 27and extends longitudinally of the metal member. The explosive charge canbe of any suitable material such as RDX, PETN, TNT or any highexplosive.

A holder or band 29 is provided for positioning the linear-shapedexplosive charge 23 with respect to the shield 11 and to the pipe 21 andis formed of a suitable flexible material such as an extruded plastic.Each side of the band is provided with spaced parallel raised portionsor beads adjacent the outer side margins of the band 29 which areadapted to receive the lower extremities of the shield sections 12 and13. As can be seen from FIGURE 2, the beads 31 and 32 snugly receive thelower extremity of the side wall portions 12b and 13b of sections 12 and13. The explosive charge 23 is disposed within an enclosed elongatechamber 33 formed in the band 29 so that it encircles the pipe 21.Suitable means is provided for securing the band 29 to the pipe 21 andcan be of the type disclosed in copending application Ser. No. 481,009,filed Aug. 19, 1965, or alternatively, it can consist of pieces ofVelcro tape which are secured to the ends of the band and then areoverlapped and fastened together in a manner well known to those skilledin the art to cause the band 29 to form a snug -fit with the pipe 21.The band 29 is, of course, positioned so that the linear shapedexplosive charge 23 is properly positioned with respect to the pipe.

A breech 36 is :formed as an integral part of the section 13 and carriesa breech block assembly 37. Toggle means is provided for releasablylatching the sections 12 and 13 about the pipe 21 and into a rigidunitary assembly and consists of a lock handle 38 which is pivotallymounted by a pin 39 in an ear 41 formed integral with section 12. AU-bolt 42 has its ends extending through a rod 43 pivotally mounted inthe handle 38 and retained therein by nuts 44. The U-bolt 42 is adaptedto engage a quick disconnect fitting 46 formed as an integral part ofthe section 13 as shown in FIGURE 1. Thus, it can be seen that when thehandle 38 is raised, the toggle is broken and the U-bolt can be readilylifted off of the fitting 46 and, conversely, when it is desired torigidly clamp the sections 12 and 13 together, it is merely necessary toplace the U-bolt 42 over the fitting 46 and then to press downwardly nthe handle 38 until the longitudinal axis of the U-bolt 42 extends belowthe center of the pin 49 to close the toggle assembly and to rigidlyinterconnect the sections 12 and 13.

The breech block assembly 37 consists of a breech block 48 which issubstantially cylindrical and which is provided with arcuate cut-outs 49and 51 provided in an annular inwardly extending flange 52 provided onthe bottom of the breech block. The cut-outs 49 and 51 are adapted toreceive the sidewise extending arcuate lugs 53 and 54 provided on thetop of the breech 36. The breech 36 is provided with a centrallydisposed bore 56 which extends therethrough (see FIGURE 2). A 'detonatorcartridge assembly 57 is adapted to be positioned in the bore 56. Thisdetonator cartridge assembly is substantially identical to the detonatorassembly disclosed in copending application Ser. No. 481,009, filed Aug.19, 1965, and as therein disclosed consists of a cartridge 58 which hasa primer 59 mounted in the upper end thereof. A sleeve 62 formed of asuitable resilient material such as rubber is mounted on the carriage. Ablasting cap 63 is mounted at the lower end of the sleeve so that it isimmediately adjacent the linear-shaped explosive charge 23 carried bythe holder 29.

A sensing pin 66 is slidably mounted in the breech 36 in a bore 67 whichextends in a direction parallel to the bore 56 in the breech. Means isprovided for spring loading the sensing pin 66 so that it is normallyyieldably urged in an inwardly direction with respect to the shield 11and consists of a spring 68 disposed in a well 69 provided in the breech36. The lower end of the spring engages a cross pin 71 mounted in thepin 66 and the other end of the spring 68 is engaged by a retaining ring72 mounted on the upper portion of the well 69. It can be seen that thesensing pin 66 is of such a length so that when the shield 11 is engagedwith the object 21 to be cut, the upper portion of the sensing pinprotrudes above the breech 36.

The breech block assembly 37 also consists of a base plate 76 which issecured to the breech block 48 by cap screws 77 (see FIGURE The baseplate 76 is provided with an arcuate slot 78 which is adapted to receivethe sensing pin 66. The base plate 76 is also formed with a smallcentrally disposed bore 79 for a purpose hereinafter described. The bore79 is provided with a chamfer 81 (see FIGURE 2) which opens into alarger bore 82 and which is also provided with a chamfer 83. A rotorplate 86 is pivotally mounted upon the base plate 76 by a pin 87. Therotor plate 86 is generally rectangular in configuration and is providedwith an open-ended slot 88 at the end remote from the pivot pin 87 whichreceives the sensing pin 66. The rotor plate 86 is also provided with anelongate slot 89 in which a firing pin 92 is disposed. The firing pin 92is provided with a shoulder 93 which is adapted to engage the uppersurface of the rotor 86. One portion 89a, of the slot 89, is of a sizewhich will permit the shoulder 93 to pass therethrough, whereas theremaining portion is relatively narrow and will not permit the shoulder93 to pass therethrough. As can be seen from FIGURES 6 and 7, the rotorplate is also provided with a ramp which inclines downwardly andinwardly from the top side of the rotor plate and which is adapted to beengaged by the shoulder 93 so that as the rotor plate is rotated aboutthe pivot pin 87 to move the rotor plate from a position in which thefiring pin 92 extends through the hole 89 to a position in which thefiring pin 92 is in the outer extremity of the portion 89b of the slot89, the firing pin is released.

Means is provided for yieldably retaining the rotor plate 86 in aposition in which the firing pin is raised or, in other words, is in asafe position and consists of a spring 94 which is mounted upon a ballplunger 96 and has one end engaging the breech block 48 and has theother end engaging the rotor plate 86. The spring 94 serves to keep therotor plate 86 in the proper alignment when the breech block assembly 37is positioned over the breech 36 such that the sensing pin 66 willengage the open end slot 88, and also to prevent the rotor plate 86 fromflopping around loosely when the breech block assembly 37 is out ofengagement with the breech 36. The ball plunger 96 serves a dualpurpose. First, it serves as a post for the spring 94. Secondly itcarries a spring-loaded ball 9611 which protrudes through the base plate76 and is adapted to engage a hole 97 in the top surface of the breechto indicate to the operator when the breech block assembly has beenproperly positioned on the breech.

The breech block 48 is provided with a bore 98 which extends verticallythrough the breech block 48. The firing pin 92 is provided with anenlarged cylindrical portion 92a which is slidably mounted in the bore98. A spring 99 is mounted on the upper portion of the firing pin 92 andhas one end engaging the upper extremity of the bore 98 has the otherend engaging the enlarged portion 92a of the firing pin 92 to yieldablyurge the firing pin 92 in a downward or inward direction.

Means is provided for triggering the firing mechanism or for controllingthe movement of the firing pin within the breech block 48 and consistsof a slider 101 which is slidably mounted in a large bore 102 providedin the breech block 48. The bore 102 extends in a direction at rightangles to the bore 98. The upper side of the slider 101 is provided witha rectangular recess 103 which is large enough to receive the lowerextremity of the enlarged portion 92a of the firing pin. The lower sideof the recess 103 is formed by a fiat planar surface 104 on which thelower extremity of the cylindrical portion 92a travels. The slider 101is also provided with a slot 106 (see FIGURE 8) and in which the firingpin 92 is disposed. The slot 106 has one portion 106a which is of such awidth that it will permit the enlarged portion 92a of the firing pin 92to pass therethrough, whereas the remaining portion 106b of the bore 106is sufiiciently narrow to prevent the passage of the enlarged portion92a therethrough. Means is provided for yieldably urging the slidertowards the safe position and consists of a spring 108, One end of whichengages the inner end of the slider 101 and the other end of whichengages the inner extremity of the bore 102.

Means is provided to permit manual retraction of the firing pin 92against the force of the spring 99 and consists of a pull ring 109connected to a short length of flexible cable 111 mounted in the outerend of the firing pin 92. Means is also provided for operating theslider 101 to cause firing of the firing mechanism and consists of acable release assembly 112. The cable release assembly consists of amale quick-release assembly 113a which mates with a female quick-releaseassembly 113b which is threaded" into the bore 102. A cable assembly 114is connected to the assembly 113a and to an operating handle 116. Thecable assembly consists of a metal pushpull control cable 117 which hasone end connected to a riged sliding member 118 mounted within thefitting assembly113zz and has the other end secured to anactivating'plunger or button 119 in the handle 116. The cable assemblyalso includes a flexible armored sheath 121 which is protected by acovering 122 of suitable material such as plastic. The handle 116consists of a cylindrical member 123 with a'large bore 124 formedtherein. The cable assembly 114 is secured to the member 123 by setscrews 126. A spring 127 is mounted in the bore 124 and has one endengaging the lower extremity of the bore and has theother-end engagingthe activating button 119 to yieldably urge the activating button andthe cable attached thereto into a retracted position. A safety button128 is mounted in the button 119 and is normally yieldably urgedoutwardly by a Spring 129 disposed in a bore 131- provided in the button119. As can be seen, the safety button 128 prevents the activatingbutton 119 from being depressed into the handle member 123 until thesafety button has been pressed inwardly to clear the member 123. Y

1 Operation and use of the explosive cutting device may now be brieflydescribed as follows. Let it be assumed that it is desired to cut a pipesuch as pipe 21 shown in FIG- URE 1. An explosive charge holder 29 withthe linearshaped explosive charge 23 therein is wrapped around the pipeso that the area immediately beneath the explosive charge 23 defines anannulus on which the cut is to be made in the pipe. The holder 29 issecured to the pipe by utilizing the Velcro tape hereinbefore described.The shield 11 is then taken and the two halves are opened up and areplaced around the pipe 21 in a position overlying the holder 29 with thesides being in alignment with the spaces provided between the beads 31and 32 on the holder29. The-U-bolt 42 is then placed over the endfitting 46 with the handle 38 in a raised position. The handlethereafter is brought downwardly until the U-bolt 42 passes over thecenter of the pivot pin 39 to securely lock the shield 11 to the pipe 21as shown in FIGURE 1. At the time that the shield is being latched intoplace onthe pipe 21, the spring-loaded sensing pin 66 engages the'holder29 and'is pushed upwardly against the force of the spring 68 so that theupper extremity of the pin 66 protrudes from the breech 36.

' After the shield 11 has been latched in place, the breech blockassembly 37 is taken and placed over the breech 36 in such a manner thatthe sensing pin 66 is disposed in the arcuate slot 78 provided in thebase plate 76. At the same time, the cut-outs 49 and 51 receive the lugs53 and 54. The'breech block assembly 37 is then rotated in a clockwisedirection as viewed in FIGURE 5 so that the lugs 53 and 54 are engagedby the flange 52 provided on the breech block 4 8. The breech blockassembly 37 must be rotatedsufliciently sothat the firing pin 92 iscleared for operation as will be apparent hereinafter. This ensures thatthe maximum interlocking lug and flange area will be engaged between thebreech block assembly and the breech to thereby prevent the breech blockassembly from being accidentally blown'off.

As can be seen from 'FIGURES -6 and 7, the breech block 48 is rotated ina clockwise direction, the sensing pin 66 which is stationary causes therotor plate 86 to be rotated about its pivot pin 87 in acounter-clockwise direction against the force of the spring 94 so thatthe portion 891': of slot 89 is moved into registration with the firingpin 92 as shown in FIGURE 7. Thus, it can be seen that if the breechblock 48 is not rotated sufliciently far enough, the firing 'pin willnot clear the rotor plate 86 and the breech block assembly 37 cannot beoperated to fire the detonator cartridge assembly 57. In the embodimentshown in the drawings, the rotation of the breech block 48 must bethrough substantially 90 before the firing pin 92 is cleared.

In the event it is desired to remove the breech block assembly 37 afterit has been placed in position, this can be accomplished by merelyrotating the breech block 48 in an opposite or counter-clockwisedirection. The in clined ramp 90 which is provided in the rotor 86engages the collar 93 of the firing pin 92 and as the rotor 86 is movedin a clockwise direction, the firing pin 92 is urged upwardly againstthe force of the spring 98 and into the portion 89b of slot 89 so thatthe firing pin cannot be fired. Thereafter, the breech block assembly 37can be removed. When the breech block assembly 37 has been rotated tothe proper place, the pin 96 drops into the recess 97 to hold the breechblock assembly 37 in the proper angular position and to prevent it fromsliding around on the breech.

As soon as the breech block assembly 37 is in place, the male assemblyor connector 113a on the end of the cable release assembly 112 isconnected into the female assembly 113b on the breech block assembly. Assoon as this has been done, the ring 109 is pulled upwardly to cock thefiring pin 92. This is accomplished by raising the firing pin 92 againstthe force of the spring 98 so that it is lifted out of the hole 106aprovided in the slider 101 and to permit the slider to be pushed to theright by the spring 108 as viewed in FIGURE 2 and so that the firing pinis disposed in portion 106!) of slot 106 and the collar 92a engages theupper surface 104 on the slider. The operator can readily tell Whethercocking has taken place because there is an audible click when thespring 108 pushes the slider 101 beneath the firing pin 92.

The cutting device is now ready to be fired. The opera tor then stepsaway to a remote location taking the handle 116 of the cable releaseassembly 112 with him to a suitable safe distance. The operator thenfires the explosive cutting device by depressing the safety button 128with one hand and then at the same time pressing inwardly with the otherhand on the large actuate button 119 to advance the cable 117 and thesliding member 118 carried thereby into the breech block assembly. Thesliding member 118 engages the slider 101 and shifts it to the left asviewed in FIGURE 2 against the force of the spring 108. Whenapproximately of an inch of movement has taken place, the portion 106aof the slot 106 in the slider 101 is moved into registration with thefiring pin 92 and permits the firing pin 92 to be rapidly urgedtherethrough under the force of the spring 98 to pass through the smallhole 79 provided in the base plate 76 and to impinge upon the primer 59to detonate the same. Detonation of the primer fires a non-electricblasting cap 63 which initiates the explosive charge 23. The initiationof the charge 23 causes cutting of the pipe as described in copendingapplication Ser. No. 481,009, filed Aug. 19, 1965. In brief, as thelinear shaped explosive charge 23 explodes, the metal jacket or sheath27 is propelled outwardly in the area that is away from the pipe andbeing cut or, in other words, in the chamber 22. Explosion in the areawhich is facing the pipe is propelled inwardly in a concentrated jet topartially penetrate the pipe. It is believed that the linear shapedexplosive charge actually causes a scoring of the pipe which causes astress concentration in the area. The shock Waves generated by thelinear shaped explosive charge and the over-pressure from the expandinggases within the shield 11 then serve to break the pipe at the point atwhich it has been scored.

After the explosive charge has been detonated and the pipe has been cut,the entire explosive cutting device can be removed. All the parts can bere-used for the next cut with the exception that a new detonatorcartridge assembly 57 will have to be provided as Will an additionallength of the holder 28 with the linear shaped explosive charge carriedthereby. The shield 11 with its breech and the breech block assembly canbe used repeatedly in making cuts in pipe or other objects.

In the design of the above identified explosive cutting device, a greatmany safety criteria have been met to make use of the explosive cuttingdevice substantially fool-proof. For example, the explosive cuttingdevice cannot be actuated unless it is mounted on the pipe to be cut.This is accomplished in two ways. First, the U-bolt 42 which locks thetwo half sections 12 and 13 together cannot be taken off of the endfitting 46 unless the breech block assembly 37 has been removed. This istrue because there is mechanical interference between the parts. Thus,to remove the shield, it is first necessary to remove the breech blockassembly 37. Second, when the shield 11 is off of the pipe, it isimpossible to fire the same because the sensing pin 66 does not projectabove the breech. Since this is the case, placement of the breech blockassembly 37 on the breech and rotation of the same will not causepivotal movement of the rotor plate 86 and, therefore, the firing pin 92will not be freed. As also pointed out previously, it is the engagementof the sensing pin 66 with the rotor 86 that causes freeing of thefiring pin.

The explosive cutting device cannot be fired unless the toggle mechanismformed by the U-bolt assembly 42 and handle 38 and associated parts iscompletely latched. This is true because until the handle 38 is moved tothe completely closed position, there is a substantial space between thetwo halves and the detonator cartridge assembly 57. For this reason, ifthe detonator assembly 57 should be accidentally fired, the linearshaped explosive charge would not be initiated. Thus, it is only whenthe detonator cartridge assembly 57 is immediately adjacent the linearshaped explosive charge 23 that the charge 23 will be initiated.

An automatic mechanic interlock is provided so that the firing pincannot be fired unless the breech block is properly engaged. As pointedout previously, this is true because unless the breech block 48 isrotated through a sufiicient angle so that the rotor plate 86 is shiftedto place the portion 89a of slot 89 in alignment with the firing pin 92,the firing pin will not be free.

All fragmentation upon explosion is contained within the shield. Thisescape of fragments is prevented in two ways. First, the charge holder28 is provided with a pair of beads on each side of the same whichengage the outer sides of the sections 12 and 13. When the linear shapedexplosive charge is initiated, the internal bead is forced out againstthe inner surface of the shield 11 to form a relatively tight seal withrespect to the shield to thereby eliminate the escape of any substantialfragments between the holder 28 and the shield 11. Second, the twosections are rigidly interconnected to prevent them from being blownapart even momentarily during the explosion to prevent escape offragments of any substantial size. In addition, the point at where thetwo halves mate with each other there is provided an overlapping of themetal that also prevents escape of fragments of any substantial size.

As explained previously, the explosive cutting device is designed sothat it can be used repeatedly and has a substantially unlimited life.

This means for releasing the firing pin has been completely shielded inthe form of the cable assembly 112 to prevent inadvertent firing. Theexplosive cutting device cannot be actuated without the use of the cableassembly 112. This is because the slider 101 is dee ly recessed withinthe breech block assembly 37 so that it is difficult to obtain acces tothe slider 101. In addition, the slider 101 must be pushed a substantialdistance before the portion 106:: of slot 106 comes into registrationwith the firing pin 92. In addition, the spring 108 which engages theslider 101 is relatively strong. Thus, it is very difiicult tophysically depress the slider 101 without the use of the cable assembly112. The force of the spring 108 and the amount of movement required forthe slider 101 are suflicient to prevent inadvertent firing in the eventthe explosive cutting device is accidentally dropped or struck.

The cable release assembly 112 is constructed in such a manner that itcan be operated only by the use of two hands. Thus, one hand must beutilized to depress the safety button 128, while the other hand isutilized to depress the actuator button 119 against he force of therelatively strong spring 127. The cable release assembly isautomatically reset because as soon as the button 119. is released, itis pushed outwardly and at the same time, the safety button 128 popsoutwardly as soon as it clears the cylindrical member 123.

In addition to the foregoing safety features, all the parts which formthe firing mechanism and the interlocks are fail-safe. That is, if theyfail, the operator still will not be subjected to an unsafe condition.

It is apparent from the foregoing that there has been provided anexplosive cutting device which has many inherent safety factors whichare very desirable for such a unit. The firing mechanism which is thebreech block assembly is relatively simple in construction and hasrelatively few moving parts which makes it less expensive to manufactureand assemble.

We claim:

1. In an explosive cutting device for cutting a tubular object, a holderencircling the tubular object at the point at which the cut is to bemade in the tubular object, said holder having a lienar shaped explosivecharge mounted therein and substantially encircling the tubular objectalong the line at which the cut is to be made in the tubular object, ashield encircling said tubular object and overlying said linear shapedexplosive charge carried by the holder, said shield being separable andincluding means rigidly latching said shield to said tubular object, andmeans carried by the shield for detonating the linear shaped explosivecharge within the shield, said means for detonating the linear shapedexplosive charge comprising a breech carried by the shield, atdetonating assembly mounted in the breech and disposed adjacent thelinear shaped explosive charge, a breech block assembly removablymounted on said breech, said breech block assembly including a firingpin, and safety means carried by said breech and said breech block toprevent the firing pin from actuating the detonating assembly unless theshield is in engagement with the article to be cut, said safety meansincluding a sensing pin mounted in the breech, means carried by thebreech for yieldably urging the sensing pin in an inward directiontowards the object to be cut so that it normally extends beyond he innerextremity of the shield, said sensing pin having a length so that whenthe shield is in engagement with the object to be cut, the outerextremity of the sensing pin extends above the breech, said breech blockassembly including a breech block, said firing pin being slidablymounted in said breech block, a rotor plate pivotally mounted on saidbreech block, said rotor plate having a slot therein, a portion of saidslot being sufiiciently large to permit the firing pin to passtherethrough and the remaining portion of said slot being of a sizewhich prevents the firing pin from passing therethrough, and meanscarried by said rotor plate and engageable by the sensing pin forshifting the rotor plate to a position in which the firing pin can passthrough the slot in the rotor plate when the breech block assembly issecured to said breech.

2. A cutting device as in claim 1 wherein said means carried by therotor plate engageable by the sensing pin includes a recess in the rotorplate engageable by the sensing pin so that as the breech block assemblyis rotated, said sensing pin cause aid rotor plate to be pivoted.

3. A cutting device as in claim 2 together with a base plate mounted onsaid breech block and underlying said rotor plate, said base platehaving an arcuate slot therein adapted to receive said sensing pin andpermitting movement of said breech block through a substantial anglewith respect to said sensing pin.

4. A cutting device as in claim 1 together with a slider slidablymounted in said breech block, said slider having a slot therein, oneportion of said slot being of a larger size to permit the firing pin totravel therehrough and the other portions of said slot being of asmaller size to prevent further travel of said firing pin through saidslider, and remotely controllable means secured to said breech blockassembly for causing movement of said slider block into a position inwhich the larger portion of said slot in said slider block is moved intoregistration with said firing pin to permit the firing pin to advancetherethrough.

5. A cutting device as in claim 4 together with means secured to saidfiring pin and extending from the breech block to permit the firing pinto be raised, and means disposed within the breech block for yieldablyurging said slider into a position in which the smaller portion of saidslot in said slider is in general alignment with said firing pin toprevent further travel of the firing pin through the slider.

6. A cutting device as in claim 4 wherein said remotely operable meansfor moving said slider includes a flexible cable, a flexible sheathsurrounding said cable, and means for causing relative movement betweensaid cable and said sheath to cause movement of said slider.

7. In an explosive cutting device for cutting a tubular object, a linearshaped explosive charge, means for securing said linear shaped explosivecharge to said tubular object so that the linear shaped explosive chargeis in general alignment with the line on which a cut is to be made inthe tubular object, a shield surrounding said tubular object andenclosing said linear shaped explosive charge, a breech mounted on saidshield, a detonator assembly mounted in said breech, a breech blockassembly removably secured to said breech, said breech block assemblyincluding a breech block, a firing pin slidably mounted in said breechblock, means including a slider mounted in said breech block fornormally retaining said firing pin in a cocked position and forreleasing said firing pin from a cocked position, means for actuatingsaid slider to move the same to a position in which the firing pin isreleased, means in the breech block for urging the firing pin intoengagement with the detonator assembly to detonate the the same, safetymeans carried by the breech and the breech block assembly and preventingsaid firing pin from detonating said detonator assembly unless saidshield is in engagement with the tubular object to be cut, said safetymeans including a sensing pin slidably mounted in said breech, meanscarried by the breech for yieldably urging the sensing pin in adirection towards the tubular object, said sensing pin being of asufficient length so that when the shield is in engagement with thetubular object, the sensing pin is disposed above the breech, a rotorplate pivotally secured to the breech block, said rotor plate having aslot therein, one portion of said slot being sufficiently large topermit further travel of said firing pin through the same, and theremaining portion of said slot being of a smaller size to preventfurther travel of the firing pin through the slot, said rotor plate alsohaving an additional arcuate groove engageable by said sensing pin, saidbreech block assembly being rotatable on said breech whereby uponmovement of said breech block assembly, said sensing pin causes movementof said rotor plate to shift said rotor plate into a first position inwhich the larger portion of said first named slot is in alignment withsaid firing pin to permit the firing pin to travel therethrough.

8. A cutting device as in claim 7 wherein said rotor plate 1s providedwith an mcllned surface ad acent said 5 slot, said surface beinginclined upwardly from the larger portion of said slot to the smallerportion of said slot in said rotor plate, said firing pin having anenlarged portion adapted to engage said inclined surface of said rotorplate.

9. A cutting device as in claim 7 wherein said sections are providedwith reinforcing webs which extend radially and are perpendicular to thesides and wherein said sections are provided with overlapping endportions.

10. In an explosive cutting device for cutting a tubular object, aholder adapted to encircle the tubular object, said holder having alinear shaped explosive charge mounted therein and adapted tosubstantially encircle the tubular object along the line at which thecut is to be made in the tubular object, a shield adapted to encirclesaid tubular object and overlying said linear shaped explosive chargecarried by the holder, said shield being comprised of at least twosections which are generally U- shaped in cross-section withsubstantially parallel sides, mean interconnecting the sections topermit movement of the same to positions adapted to encircle the tubularobject and to provide two free ends which are in relatively closeproximity to each other, non-yieldable latching means secured to saidfree ends of said sections for removably securing said sections to saidtubular object and means carried by the shield for detonating the linearshaped explosive charge within the shield, said shield being spaced fromthe linear shaped explosive charge so there is no direct contact betweenthe linear shaped explosive charge and the shield, said shield beingconstructed so that it arrests the travel of substantially all of anysolid particles within a limited distance in at least one directionwhich are propelled by the detonation of the linear explosive charge.

11. A cutting device as in claim 10 wherein said means for detonating alinear shaped explosive charge consists of a breech carried by theshield, a detonating assembly mounted in the breech and disposedadjacent the linearshaped explosive charge, a breech block assemblyremovably mounted on said breech, said breech block as sembly includinga firing pin, and safety means carried by said breech and said breechblock to prevent the firing pin from actuating the detonating assemblyunless the shield is in engagement with the object to be cut.

12. A cutting device as in claim 10 wherein said nonyieldable latchingmeans includes an over-center toggle mechanism.

13. A cutting device as in claim 12 wherein said overcenter togglemechanism comprises a fitting, linkage means engaging said fitting, saidfitting and said linkage means being of such a size and being positionedso that said linkage means cannot be removed from said fitting when saidbreech block assembly is in position on said breech.

References Cited UNITED STATES PATENTS 2,140,338 12/1938 Temple.

2,638,323 5/ 1953 Bannon.

2,846,968 8/1958 Tipton 113-402 3,089,417 5/1963 Beyer et al. 102-243,135,163 6/1964 Mechlin et al. 10224 3,169,479 2/1965 Bryan 102-243,336,868 8/1967 Rush et al. 10224 SAMUEL W. ENGLE, Primary Examiner.

